ZOE Kazan has two mom mies. There’s her real mom, Robin Swicord, writer/director of the upcoming film “The Jane Austen Book Club.”

And then there’s poor Theresa, the single mom and chambermaid whom Janel Moloney – Donna Moss in TV’s “The West Wing” – plays in “100 Saints You Should Know,” opening tonight at Playwrights Horizons.

Poor Theresa, indeed. Kazan’s character – 16-year-old Abby – is a hellion, a bad seed with an iPod and attitude to spare.

So brutal is the onstage battle between mom and daughter that, when you meet them for lunch, you’re tempted to hide the knives.

Alas, they’re only acting. They really like each other. They really, really like each other.

“If we were mother and daughter, we’d have a really, really good relationship,” says Moloney, 37, who’s 13 years older than the Yale grad who plays her daughter. “She’s highly motivated and supersmart.”

Not to mention well connected. Zoe’s grandfather was writer/director Elia Kazan (“By the time my sister and I were born, he kind of mellowed with age,” she recalls), and her father, Nicholas Kazan, is a director, too.

Moloney has connections, too. Her aunt, Christine Ebersole, won a Tony for “Grey Gardens.”

“She’s thrilled for me,” says Moloney. “I called her a couple of times when I wasn’t sure about where I was in the process, and she just told me to hang in.”

And no, says the willowy blonde – who lives across the street from her “West Wing” co-star Allison Janney when she’s in L.A. – she never expected to make her New York stage debut cleaning a toilet, as she’s doing when the curtain rises on “100 Saints,” Kate Fodor’s play about faith and connection.